Various wireless communication systems such as PDC (Personal Digital Cellular), W-CDMA (Wideband Code Division Multiple Access), cdma2000 1x, PHS (Personal Handy-phone System), wireless LAN (Local Area Network) and Bluetooth have been operated conventionally as mobile communication systems. In addition, standardization of high-speed wireless communication such as LTE (Long Term Evolution), WiMAX (Worldwide Interoperability for Microwave Access), UMB (Ultra Mobile Broadband) has been in progress. Each of these wireless communication systems has different characteristics.
PHS, for example, has an advantage of high frequency usage efficiency as capable of taking numerous usable terminals per unit area because of its small cell area. In addition, since a PHS terminal needs to receive only individual call signals (PCH: Paging Channel) while capturing a cell station (CS) and intervals thereof are long, it has also an advantage of a long standby time. However, because the area covered by a single cell is small, there is a disadvantage of high possibility of disconnection of communication if the PHS terminal performs communication moving at a high speed.
In contrast, W-CDMA, for example, has a wide cell area and thus enables a W-CDMA terminal to communicate moving in a wide area at a high speed. However, since the W-CDMA terminal performs despread processing and the like for monitoring an incoming call and a signal level of a cell and the like, its standby time is much shorter than that of the PHS terminal.
Wireless LAN typified by widely used IEEE (Institute of Electrical and Electronic Engineers) 802.11b has its hotspots installed in coffee shops, public facilities and the like and can communicate at rates up to 11 Mbps. However, such wireless LAN is provided on the assumption of indoor use and thus a cell area thereof is small such as about 10 m in radius.
It has also been considered recently to provide a multi-mode mobile communication terminal capable of using different wireless communication systems seamlessly. For example, there is known a mobile communication terminal which changes the wireless communication systems based on a moving speed thereof or depending on a remaining battery level and a determination on length of the standby time in each of a plurality of wireless communication systems (see Patent Document 1, for example).    Patent Document 1: Japanese Patent Laid-Open No. 2004-235863